Definition 1:
Excessive and tedious study used so that students with little more than hot air between their ears can keep up with the smarter ones. It's pretty much an excuse to reword someone else's work using a bibliography.

Definition 2:
An uncommon slang term for masturbation. Often said in a "sarcastic" way.

Def 1:
Man, the mental kid has a better grade than me! He must do a lot of research!